The present disclosure is related generally to the field of biofuels, and more specifically but not exclusively, to producing monoalkyl fatty acid esters or biodiesel from triglyceride feedstocks.
It is commonly recognized that natural triglyceride sources include some fraction of free fatty acid. Low value materials such as brown grease, trap grease and sewage plant float grease may have free fatty acid contents as high as 80% w/w or more. Triglyceride feedstocks with high free fatty acid fractions are poor starting materials for the production of biodiesel or other fatty acid ester products unless the free fatty acid fraction can be converted to product esters prior to the conversion of the triglycerides into fatty acid esters. In general, methods to convert high free fatty acid feedstocks to biodiesel generally involve multiple steps, extreme temperatures or long residence times, none of which are conducive to a continuous flow process.